1. Field of the Invention
The present invention relates to a delivery device for injecting drugs, vaccines, and the like into the intradermal region of the skin.
2. Description of Related Art
There are several injection techniques and devices known in the art. Based on the drug substance being injected, one technique and device may provide for a more efficacious delivery and uptake of the particular drug substance. One technique and device delivers a drug substance intramuscularly using a hypodermic needle that penetrates through a patient's skin and into muscle tissue.
Another technique and device delivers a drug substance into the subcutaneous region of the skin. It is possible that the same device may be used to delivery an intramuscular and a subcutaneous injection, with the health care provider controlling the depth of the injection.
Techniques and devices are also known for administering an injection into the intradermal (intradermal) region of the skin. One technique, commonly referred to as the Mantoux technique, uses a “standard” syringe, i.e., a syringe typically used to administer intramuscular or subcutaneous injections. The health care provider administering the injection follows a specific procedure that requires a somewhat precise orientation of the syringe with regard to the patient's skin as the injection is administered. The health care provider must also attempt to precisely control the penetration depth of the needle into the patient's skin to ensure that it does not penetrate beyond the intradermal region. Such a technique is complicated, difficult to administer, and often may only be administered by an experienced health care professional.
Devices have been proposed for providing intradermal injections which include shortened fine gauge needles compared to conventional needle sizes. The smaller needles are not intended to penetrate beyond the dermis layer of the skin. Such devices are shown in U.S. Pat. No. 5,527,288 to Gross et al., U.S. Pat. No. 4,886,499 to Cirelli et al., and U.S. Pat. No. 5,328,483 to Jacoby. The proposed devices, however are not without shortcomings and drawbacks.
For example, the devices shown in U.S. Pat. Nos. 5,527,288 and 4,886,499 are highly specialized injectors. The designs for these injectors include relatively complex arrangements of components that cannot be economically manufactured on a mass production scale. Therefore, such devices have limited applicability and use.
For many drug substances, it may be desirable to fill the delivery device at the point of, and immediately prior to use. In this situation, the delivery device is normally filled from a multi-dose vial. A multi-dose vial may be more economical and it enables the user to fill the delivery device with the specific dose required. The multi-dose vial may be pre-filled with a liquid substance or with a dry substance. For example, it is now conventional to reduce certain drugs to a dry or powdered form to increase the shelf life of drugs and reduce inventory space. Multi-dose vials are typically sealed with an elastomeric stopper or septum. A needle on the delivery device may be used to pierce the stopper or septum and draw the drug substance from the vial into the delivery device, typically a syringe. The drug substance may then be administered using the delivery device, which is discarded after use, and the unit-dose vial may be stored for further use.
As advances in understanding the delivery of drug proceeds, the use of intradermal delivery systems is expected to increase. Use of a “standard” length needle to deliver a drug substance intradermally has its shortcomings, come of which are identified above. It is not possible to use a delivery device having a needle length suited for intradermal injection to aspirate a syringe with drug substance from a multi-use vial. Thus, there are shortcomings in the prior art that prevent administering an intradermal injection using a “standard” length needle and a multi-use vial. It would be advantageous to have a drug delivery device capable of accessing substances stored in multi-dose vials and delivering such substances into the intradermal region of the skin without encountering the shortcomings described above.
FIG. 1 shows an intradermal injection device 101 comprising a syringe 114 having a syringe body 116 that defines a reservoir 118 within which a drug substance may be held, a plunger 120 disposed in the syringe body 116 and having a flange 122 at a distal end thereof and a stopper 124 at the opposed proximal end thereof, and a needle assembly 102 secured to a distal end of the syringe body 116. An exemplary needle assembly 102 of the type depicted in FIG. 1 is disclosed in U.S. Pat. No. 6,494,865 to Alchas, the entire contents of which is incorporated by reference herein. The needle assembly 102 is specifically designed for making intradermal injections. The needle assembly 102 may carry a needle cannula 104 having a needle tip 106 at a distal end thereof. Alternatively, the needle cannula 104 may be secured directly to the syringe body 116. The needle assembly 102 also includes a penetration limiter 108 having a hub portion 109 that may be secured to the syringe body 116, and a limiter portion 111 that defines a generally flat skin engaging surface 110 at a distal end of the limiter 108. The limiter 108, which generally surrounds the proximal end of the needle 104, permits a certain predetermined length of the needle cannula 104, including the needle tip 106, to protrude beyond the skin engaging surface 110 so that the distance between the needle tip 106 and skin engaging surface 110 limits penetration of the needle tip 106 into the intradermal space of the patient's skin. Preferably, the needle tip 106 of the needle cannula 104 extends beyond the skin engaging surface 110 a distance ranging from approximately 0.5 mm to 3 mm. The needle cannula 104 and skin engaging surface 110 are also arranged with respect to each other in a generally perpendicular relationship that serves to ensure a generally perpendicular relationship between the needle cannula 104 and the patient's skin; such an angular relationship being preferred when making intradermal injections. The skin engaging surface 110 engages the surface of the skin of a patient and limits the penetration depth of the needle tip 106 into the patient's skin. The needle assembly 102 is secured to the syringe 114 via the hub portion 109, which may be fixedly secured to the syringe body 116, or the hub portion 109 may be secured by a Luer fit or equivalent attachment method.
Referring now to FIG. 2, a conventional syringe 114 being filled from a multi-use vial 126 is shown. The vial 126 includes an open end, a rim surrounding the open end and a reduced diameter neck portion adjacent the rim. The vial 124 is typically sealed with an elastomeric septum 128 which includes a portion inserted into the neck of the vial 126 and a planar rim portion which overlies the vial rim. The septum 128 is normally secured to the vial rim with an aluminum collar 130. In FIG. 2, a conventional syringe 114 is being used to access a drug substance contained within the vial 126. The needle 104 in this case is sufficiently long to penetrate the septum 128 to access the drug substance contained in the vial 126.
As may be appreciated from FIGS. 1 and 2, it is not possible, using a device having a stationary limiter, to fill a reservoir from a conventional vial. The distance d is too short to adequately penetrate the depth of the septum and access the substance contained in the vial. The present invention allows for access to a substance contained in a conventional vial by an intradermal needle device or assembly. As a result, there is no need to pre-fill an intradermal device of the present invention prior to use. Thus, standard methods for preserving the therapeutic and/or diagnostic substances, such as maintaining them in liquid or powder form in conventional vials for future use, may be used with the intradermal devices of the present invention. Furthermore, using the intradermal devices of the present invention, it is possible to use conventional, inexpensive delivery devices such as plastic syringes, in conjunction with the intradermal devices, which are often not appropriate for use as pre-filled devices.
In light of the above, there is a present need for a drug delivery device intradermal that enables a user to fill the intradermal device with a drug substance at the time of use by aspiration from a multi-dose vial, and to administer an injection into the intradermal region of the skin easily and repeatedly and without relying on the experience of the health care professional administering the injection.